[ZX5focused]

direct injection, the fuel is injected directly into the cylinders where as in fuel injection it is misted into a mixture with the air before it reaches the combustion chamber (before the intake valves).

thats the basics of it.

edit:
wikipedia:

Gasoline direct injection or GDI is a variant of fuel injection employed in modern four stroke petrol engines. The gasoline or biobutanol is injected right into the combustion chamber of each cylinder, as opposed to conventional multi point fuel injection that happens in the intake manifold.